Resonant circuit



Patented Oct. 17, 1950 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 9 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to resonant structures, and more particularly to cavity-resonators for ultrahigh frequency work.

The primary object of the present invention is to generally improve ultrahigh frequency oscillators. Another object is to improve ultrahigh frequency oscillators using lighthouse tubes. Still another object is to improve ultrahigh frequency oscillators of the cavity resonator tylpe. Considered in another aspect, an object of the present invention is to combine these ideas to provide an ultrahigh frequency oscillator of the cavity resonator type using a tube of the lighthouse type.

With these objects in View I provide two cavity resonators acting as input and output circuits connected to the electrodes of the tube. When the apparatus is used as an oscillator these resonators are regeneratively coupled. In accordance with a further feature and object of the invention, conveniently accessible and easily operated tuning means are provided for independently expanding or contracting each of the resonators.

To accomplish the foregoing and other objects which will hereinafter appear, my invention resides in the cavity elements and their relation to the electron tube intended to be used therewith, as hereinafter are more particularly described in the specification and sought to be defined in the claims. The specification is accompanied by a drawing in which:

Figure 1 is a partially-sectioned and partiallyschematic illustration of apparatus embodying features of my invention, said section being taken approximately in the plane of the line I-I of Figure 2;

Figure 2 is a plan view of the same;

Figure 3 is an enlarged section taken in substantially the same plane as Figure 1, and showing tuning means; and

Figure 4 is a fragmentary section through the cavity resonator wall, and explanatory of a detail.

Referring to the drawing, the present apparatus comprises neighboring metal cavity resonators I2 and I4, connected at their adjacent walls as is indicated at I6. The resonators are used with an electron tube including a cathode I8, a grid 20, and an anode 22. In the specic case here illustrated, the grid 2B is connected to the inner walls '24 and 26, while the outer walls are cically, the outer wall 28 is capacitively coupled to the cathode I8 through the base portion $0 of the tube, and the outer wall 32 of cavity l2 is capacitively coupled through an insulation collar 34, preferably made of polystyrene, to the anode terminal 3B of the tube. In this way, the resonator l2 acts as a resonant circuit connected between the grid and the anode of the tube, while the resonator I4 acts as a resonant circuit connected between the grid and the cathode of the tube.

The specific structure here illustrated is designed for use with a so-called lighthouse tube. Such a tube comprises an envelope made up of two cylindrical glass portions 40 and H2, sealed together at a metal ring 44, said ring carrying the wires of grid 20, and acting as a grid terminal. The cathode I8 projects upwardly from the base 46 to a point very close to the grid, it being understood that the cathode is hollow, and indirectly heated by an appropriate internal heating lament. The anode 22 depends from the top of the tube to a point near the grid, and its upper end forms the anode terminal 36. The radiofrequency connection to the cathode is made capacitively by means of a metal sleeve 38 clamped about and forming a part of the base of the tube. It is to be understood that the resonators may be used with other types of tubes, and particularly with tubes having axially-spaced electrode terminals.

In the illustrated form of the invention, the walls of resonators I2 and Hl are appropriately apertured to receive the lighthouse tube, the latter passing through the resonators. The aperture in wall 24 is large enough to receive the upper part of the tube but is too small to -pass the ring 44, and these parts are held in electrical contact. In Figures 1 and 2 it will be seen that the resonator assembly is iixed in desired position over the tube by means of a suitable bracket 50, the inner end of which is secured between the adjacent resonator walls, and the outer end of which is fastened to a panel 52 by means of screws 54. The tube is received in a conventional tube socket 5E, screwed to a chassis plate 58. To change tubes it is necessary to release screws 54 and elevate the resonator assembly, or to remove screws 51 and lower the socket, whereupon the tube may be removed and replaced.

In Figure l, the capacitive coupling of the upper resonator to the anode terminal is schematically illustrated at 60, and the capacitive coupling of the lower resonator to the cathode is schematically illustrated at 62. It will be understood, however, that in practice the connection at 62 may be a direct metal to metal contact, because the outer metal sleeve 30 of the tube is not itself conductively connected but only capacitively coupled to the cathode of the tube. The cap-acitance provided in both cases is large enough to act substantially as a short-circuit for the extremely high frequencies here involved.

The resonator assembly is preferably provided with tuning means, one form of which is illustrated in Figure 3. For this purpose I have provided the upper resonator I2 with a hollow screw 64, which surrounds and is rotatively carried on insulation collar 34. The inner edge of the aperture in the top wall 32 is threaded to mate with screw B4, and the screw mav be provided with a knurled handle 66 for rotating the same. The threaded edge of the resonator may be thickened and reenforced by a ring 68. It will be evident that rotation of the screw will move the upper wall of the resonator in an axial direction, thereby expanding or contracting the resonator. In order to simplify the problem of anchoring the screw $4 on the tube, the upper resonator I2 is preferably designed to be normally contracted. It therefore holds the screw downwardly against the uplper end of the tube, and the screw may be used to pull the upper wall upwardly until the resonator is expanded to proper dimension.

Another hollow screw surrounds and is rotatable on the bese portion of the tube, and the aperture in bottom wall 28 of the lower resonator |4 is threaded to mate with screw 1D. Here again. the thin sheet metal of the wall is preferably thickened and reenforced by means of a threaded ring '12. The outer end of the screw is provided with a knurled handle 14. In this case the resonator is preferably made normally expanding, that is, its dimension in repose is equal to at least the maximum resonator dimension. The resonator therefore holds the screw downwardly against step 'I6 of the base. Rotation of the screw may be used to push the bottom wall upwardly until the resonator has been compressed to desired dimension.

Although other shapes may be used, I prefer to make the resonators circular in plan, as here illustrated. The resonators are approximately hollow discoids, although the peripheral portion may, if desired, be given a somewhat toroidal configuration, as indicated at 18 for the upper cavity, The illustrated discoidal shape is convenient because'it may he formed by spinning thin sheet metal to dished configuration, two such dished pieces being secured edge to edge for each cavity. If desired, the edges may be outwardly flanged, as indicated at 8|] in Figure 3. These flanges have been omitted in Figure 1 because from the electrical viewpoint they are unnecessary, and are provided only for structural convenience. The discoidal shape also has the merit that the resonators are relatively sturdy and rigid against lateral deformation. yet because the top and bottom walls are relatively flat, they are readily flexed in an axial direction to change the volume of the resonators. Still another advantage of the relatively flattened shape here illustrated, even if not discoidal, is that the horizontal walls of the resonator may be spaced at approximately correct location for coupling them to the lighthouse tube electrodes without necessitating wiring connections.

The anode of the tube is supplied with directcurrent potential through a connection 82 leading through hollow screw B4 to the anode terminal 36. Inasrnuch as the anode terminal as now made is comparatively short, the terminal is preferably extended upwardly in any desired manner, as by means of a post 84, the lower end of which is threadedly received in the upper end of terminal 36, and the upper end of which receives a spring connector 86.

When the device is used as an amplifier, it is preferably provided with input and output loops. For example, resonator I4 may be provided with an input loop 9G connected to a suitable line, in

this case a coaxial transmission line 92, whilethe resonator I2 may be provided with a suitable output loop at 94 leading to a preferably coaxial line 96. If the device is to be used as an oscillator, it is desirable to provide means for regeneratively coupling the two resonators. One method of doing this is to provide a coupling loop 98 extending through the adjacent walls 24 and 26 of the resonators, said loop being suitably positioned and dimensioned to provide the desired feedback. Another method is to provide two coaxial transmission lines which are then connected together externally of the resonators. This is shown by a third coupling loop |00 and its coaxial line |02. It will be understood that in such case the internal loop 98 may be omitted, and instead the external lines 92 and |02 are connected together for feedback. In that case, the loop 94 may be used as a pick-up loop for delivering the output of the oscillator.

In all cases the loops and transmission lines are properly located for most convenient use. They have all been shown in a single plane in Figure 3 for clarity of illustration, but in Figure 2 the lines 92, 96, and |02 are shown projecting in quadrature, which may be done if it is desired to separate the various lines as far as possible. Other directions may be used for convenience.

The resonator wall is preferably made of a suitably soft conductive metal, preferably copper.

If desired, the copper wall IM may be internally plated with silver, as is illustrated at |06 in Figure 4. The silver plating is preferably of a thickness corresponding to the depth of radiofrequency penetration of the metal. Silver plating will raise the Q of the cavity, and a Q of several thousands is obtainable.

It is believed that the method of constructing and using, as well as the advantages of my irnproved resonant structure, will be apparent from the foregoing detailed description thereof. It will also be apparent that while I have shown and described my invention in several preferred forms, changes and modifications may be made in the structure disclosed without departing from the spirit of the invention, as sought to be defined in the following claims.

I claim:

1. A resonator unit for use as an amplier or an oscillator, said unit comprising two mechanically-independent, hollow-discoidal metal cavity resonators disposed face to face with the adjacent walls in contact, an electron tube having a cathode, anode, and grid, means connecting the grid of said tube to the aforesaid contacting walls, means coupling one outside wall to the cathode of said tube, means coupling the other outside wall to the anode of said tube, and adjustable tuning means connected to said walls for independently moving the aforesaid outside walls in order to expand or contract the resonators.

2. A resonator unit comprising a pair of cavity resonators and a lighthouse-type tube, said resonators being disposed in face-to-face relation, said lighthouse tube extending through said resonators, the adjacent Walls of said resonators being disposed at and coupled to the grid terminal of the tube, the outer Wall of one of said resonators being coupled to the cathode of the tube, the outer wall of the other resonator being capacitively coupled to the anode terminal of the tube, a rst screw adjusting means at the base portion of the tube for axially moving the outer wall of the grid-to-cathode resonator and thereby expanding or contracting said resonator, and a second screw adjusting means at the anode portion of the tube for axially moving the outer wall of the grid-to-anode resonator and thereby expanding or contracting the said resonator.

3. A resonator unit for use as an amplifier or an oscillator, said unit comprising a pair of cavity resonators and a lighthouse-type tube, said resonators being disposed in iace-to-face relation and being suitably apertured to receive the lighthouse tube, said tube extending through said resonators, the adjacent walls of said resonators being disposed at and coupled to the grid terminal of the tube, the outer wall of one of said resonators being coupled to the cathode of the tube, the outer wall of the other resonator being coupled to the anode terminal of the tube, a first screw adjusting means rotatable at the base portion of the tube for axially moving the outer wall of the grid-to-cathode resonator and thereby expanding or contracting said resonator, and a second screw adjusting means rotatable at the anode portion of the tube for axially moving the outer Wall of the grid-toanode resonator and thereby expanding or contracting the said resonator.

4. A resonator unit comprising two hollow discoidal metal cavity resonators disposed face-toface with the adjacent walls electrically connected together, the adjacent and outer walls being centrally apertured with apertures of suitable dimension to receive a lighthouse tube extending axially through the resonators, the connected walls resting on and being electrically connected to the grid terminal of the tube, a hollow screw rotatably carried at the base portion 0f the tube, the aperture in the bottom wall of the lower resonator being threaded to mate with said screw whereby the dimension of the lower resonator may be adjusted by rotation of the screw, an insulation collar at the anode terminal, and a second hollow screw rotatably carried on said insulation collar, the aperture in the top wall of the upper resonator being threaded to mate with said screw, whereby rotation of the screw adjusts the dimension of the upper resonator.

5. A resonator unit comprising two hollow discoidal metal cavity resonators disposed face-toface with the adjacent walls electrically connected together, the adjacent and outer walls being centrally apertured with apertures of suitable dimension to receive a lighthouse tube extending axially through the resonators, the connected walls resting on and being electrically connected to the grid terminal of the tube, a hollow screw rotatably carried at the base portion of the tube, the aperture in the bottom wall of the lower resonator being threaded to mate with said screw whereby the dimension of the lower resonator c may be adjusted by rotation of the screw, an insulation collar at the anode terminal, a second hollow screw rotatably carried on said insulation collar, the aperture in the top wall of the upper resonator being threaded to mate with said screw,

whereby rotation of the screw adjusts the dimension of the upper resonator, the bottom wall of the lower cavity being coupled to the cathode of the tube, the top wall of the upper resonator being capacitively coupled to the anode of the tube, and a direct-current supply connection passing through the center of the upper hollow adjusting screw to the anode terminal of the tube.

6. A resonator unit for use as an amplier, said unit comprising two hollow discodal metal cavity resonators disposed face-to-face with the adjacent walls electrically connected together, the adjacent and outer walls being centrally apertured with apertures of suitable dimension to receive a lighthouse tube extending axially through the resonators, the connected walls resting on and being electrically connected to the grid terminal of the tube, a hollow screw rotatably carried at the base portion of the tube, the aperture in the bottom wall of the lower resonator being threaded to mate with said screw whereby the dimension of the lower resonator may be adjusted by rotation of the screw, an insulation collar at the anode terminal, a second hollow screw rotatably carried on said insulation collar, the aperture in the top wall of the upper cavity being threaded to mate with said screw, whereby rotation of the screw adjusts the dimension of the upper resonator, the bottom wall of the lower resonator being coupled to the cathode of the tube and the top wall of the upper resonator being capacitively coupled to the anode of the tube, a direct-current supply connection passing through the center of the upper hollow adjusting screw to the anode terminal of the tube, and coupling loops in said cavities.

'7. A resonator unit for use as an oscillator, said unit comprising two hollow discodal metal cavity resonators disposed face-to-face with the adjacent walls electrically connected, the adjacent and outer walls being centrally apertured with apertures of suitable dimension to receive a lighthouse tube extending axially through the resonators, the connected walls resting on and being electrically connected to the grid terminal of the tube, a hollow screw rotatably carried at the base portion of the tube, the aperture in the bottom wall f the'lower resonator being threaded to mate with said screw, whereby the dimension of the lower resonator may be adjusted by rotation of the screw, an insulation collar at the anode terminal, a second hollow screw rotatably carried on said insulation collar, the aperture in the top wall of the upper resonator being threaded to mate with said screw, whereby rotation of the screw adjusts" the dimension of the upper resonator, the bottom wall of the lower resonator being coupled to the cathode of the tube and the top wall of the upper resonator being capacitively coupled to the anode of the tube, a direct-current supply connection passing through the center of the upper hollow adjusting screw to the anode terminal of the tube, means regeneratively coupling one of said resonators'to the other for self l, oscillation, and a pick-up loop in one of said resoi nators for delivery of power from the oscillator.V

8. A resonator unit for an electron tube having at least two axially spaced electrode terminals, at least one of said terminals having a lateral projection, said unit comprising a metal cavity resonator having a pair of outer walls spaced apart an amount approximately equal to the spacing between the terminals, said outer Walls being apertured so that each wall is adapted to be juxtaposed to one of said terminals and electrically coupled thereto, and a hollow screw adapted to be rotatably carried by one of the terminals and to press against the projection, the aperture in the wall of said resonator which is coupled to said one terminal being threaded to mate with said screw, said last-mentioned wall being flexible whereby said screw is pressed against the projection when said wall is exed, the dimensions of said resonator being adjustable by rotation of said screw.

9. A resonator unit for an electron tube having at least three external, axially spaced electrode terminals, the two outer terminals having laterally disposed projections, said unit comprising two superposed, separable, mechanically-independent, metal cavity resonators having adjacent walls in contact and each having an outer wall, the spacing between the adjacent and the outer walls being approximately equal to the spacing between the terminals, said adjacent walls and each of the two outer walls being apertured so that they are adapted to be juxtaposed to said three terminals respectively and electrically coupled thereto, and a pair of hollow screws each being adapted to be rotatably carried by one of REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date v 2,167,201 Dallenbach July 25, 1939 2,284,405 McArthur May 26, 1942 2,404,261 Whinnery July 16, 1946 2,409,608 Anderson Oct. 22, 1946 2,412,997 Litton Dec. 24, 1946 2,427,693 Ryder Sept. 23, 1947 2,446,829 Hergenrother Aug. 10, 1948 2,463,519 Cooke et al Mar. 8, 1949 Certcate of Correction Patent No. 2,525,806 October 17, 1950 BEVERLY KUMPFER It is hereby oertied that error appears inthe printed speeicaton of the above numbered patent requiring correetlon as follows:

Column 6, line 3, for the Word cavity read resonator;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the oase in the Patent Oce. Signed and sealed this 23rd day of January, A. D. 1951.

[SEAL] THOMAS F. MURPHY,

Assistant 'ommz'ssz'ouer of Patents, 

